Was there any watering done other than the one fill-up of the watering bag? This might be excessive drought stress, as most of Maryland is either abnormally dry or in drought currently. Newly-installed plants need close monitoring for watering needs at least twice a week or more in the weather we've had recently. The Itea wilting could be the same drought stress issue, or just an infection that needs to be pruned out. We don't see indications of a particular pathogen in the photos. We do see what looks like landscape fabric used under the mulch, which we would suggest be removed. The fabric makes monitoring for watering needs difficult (since you'd need to be able to feel the soil about six inches deep next to the roots), may trap heat next to surface roots, interfering with evaporative cooling, and might also reduce the available oxygen to the soil below, to the detriment of roots and beneficial soil microbes. (More research needs to be done about the latter impact.)

Landscape fabric also isn't a great long-term solution to weed control, since weeds can eventually germinate on top of it, and if the roots of desirable plants weave into and above it as they grow, that can make later removal of the material very hard to do without damaging lots of roots in the process.

If the Lindera died due to a root rot or crown rot infection, or opportunistic infection like Botryosphaeria, then nothing can be done except to replant, since there is no fungicide useful in those situations. The site conditions are probably fine for the plants, as long as it's not excessively soggy or too drought-prone.

This wilting and die-off would probably not be due to Jumping Worm impacts, if they are indeed present.

Miri

I did water after planting every day for a few days, then every 2-3 days, then tapered off as the plants looked fine except the spicebush. I watered that once it started looking droopy but that didn’t help which is why I assumed it was diseased.

Thank you for the additional clarification; we had interpreted your "lengthy travel" mention as implying that the plants might not have been getting watered (or checked for watering needs) during that time. While research on water-retentive gels used in materials like "moisture control" potting mixes have not demonstrated effective moisture release to the plant roots, if you found that the soil remained moist several inches below the tree diapers, then perhaps their moisture release was sufficient.

Plants can wilt when over-watered as well as under-watered, as well as when a root rot or similar infection has killed roots or clogged water-conducting tissues in the main stem. That might have been what happened with the Lindera. Organisms that kill roots tend to take advantage of plants under stress, either from overly-wet soil, improper soil pH, or root injury from digging or planting. In this case, it's hard to tell what the original stressor may have been, or if the Lindera was accidentally over-watered or not. Soil pH was probably not a factor in this case, since no nearby plants are showing indications of a nutrient deficiency from soil that isn't acidic enough.

You should be able to replant, though it might be worth checking the soil by hand and watering manually for a time instead of using the tree diaper around a new Lindera, just in case it was not providing adequate moisture to its root zone. Plants also sometimes have the beginnings of an infection (like root rot) that doesn't become symptomatic until the plant experiences more stress, like from high heat (and thus a greater demand on the roots).

Miri

That's helpful--thanks! I will check the soil. I did have friends check and water while I was gone but it was very hot and dry as you mentioned, so I was hoping the tree diapers would cover any gaps.

You're welcome.